Explosive charge with annular ignition gap

ABSTRACT

An explosive charge separated from an annular propagation charge by a conical inert element so as to form an annular ignition gap between the propagation charge and the explosive charge, the annular ignition gap having a width of only 1-5 mm.

U Umted States Patent 1 91 1111 3,736,875 Bucklishch 1 1 June 5, 1973 [54] EXPLOSIVE CHARGE WITH ANNULAR 3,100,445 8/1963 Poulter ..102/24 HC IGNITION GAP 3,103,882 9/1963 Gilliland ....102/24 HC 3,443,518 5/1969 Cross 1 ..102/24 HC [75] Inventor: Ludwig Bucklishch, A-4866 Un- 3,451,339 6/1969 Precoul ..102/24 HC terach, Austria [73] Assignee: Dynamite Nobel Aktiengesellschaft, FOREIGN PATENTS OR APPLICATIONS Troisdorf, Germany 1,571,283 5/1969 Germany ..102 24 HC [22] Filed: Sept. 23, 1970 21 APPL 74,301 Primary ExaminerVerlin R. Pendegrass Attorney-Craig and Antonelli [30] Foreign Application Priority Data Sept. 23, 1969 Germany ..P 19 48 058.1 [57] ABSTRACT An explosive charge separated from an annular 52 us. (:1. ..102 24 uc, 102/56 Propagation charge y a conical inert element 80 as to [51] Int I I N F42) 13/08 form an annular ignition gap between the propagation [58] Field of HC 56 charge and the explosive charge, the annular ignition g p having a width of y 1-5 mm [56] References Cited 9 Claims, 1 Drawing Figure UNITED STATES PATENTS 2,892,407 6/1959 MacLeod ..102/24 HC PATENTEDJUH 5 I973 3,736,875

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INVENTOR LUDWIG BUCKLISCH mwgmxmmsmm- A axgsp EXPLOSIVE CHARGE WITH ANNULAR IGNITION GAP The present invention relates in general to explosive charges, and particularly to a symmetrical explosive charge having an annular ignition gap.

Annular initiating devices are employed in the case of rotationally symmetrical explosive charges, and are used preferably in hollow explosive charges. These are blasting charges of a predominantly cylindrical shape exhibiting a recess on the side thereof facing the object to be blasted, which recess is normally lined with a layer of metal or other material. The ignition of such hollow explosive charges must be initiated from the end opposite the recess. The igniting element can be disposed centrally on the axis of the explosive charge or can also be arranged annularly at the outer rim thereof. The latter design makes it possible to control the detonation waves so that they extend annularly from the outside toward the inside in the direction toward the recess, which is most advantageous. In order to accomplish this objective, inert bodies ofa disk-like or conical shape are normally provided between the central primer and the hollow explosive charge, the detonation being triggered by the primer extending around the inert body. This construction makes it possible to obtain advantages for special purposes with respect to the effect of the spatial dimensions of the explosive charge.

It is well known that any irregularity in the path of the detonating process considerably reduces the efficiency of such hollow explosive charge. An irregular path of the detonation can be caused by the eccentric position of the central primer, and, in case of annular priming, by an eccentric arrangement of the inert component with respect to the axis of the hollow explosive charge. In the conventional hollow explosive charge, the blasting charge disposed behind the inert component and employed for the transmission of the detonation is relatively thick. The thickness of this conical or cylindrical propagation charge is normally l-l5 mm. and more, and additionally, widens toward the hollow explosive charge, because the inert component is rounded toward the bottom surface. Consequently, the annular aperture between the propagation charge and the hollow explosive charge is relatively wide, being generally 2 cm. and more. This entails numerous disadvantages. Due to the propagation charge of excessive width behind the inert component, the ignition of the detonation can occur, on one side, to a larger extent toward the inner diameter, and, on the other side, more at the outer rim, and a varying initiation of the hollow explosive charge is the consequence. Besides, due to the very thick propagation charge, a strong pressure is also exerted on the inert element, which pressure can prematurely destroy this inert element, or alter the position thereof. Consequently, the progression of the detonation becomes even more irregular.

Detailed investigations have shown that, in case of annular ignition of axially symmetrical explosive charges, the explosive propagating charge disposed behind the inert component is to be as small as possible, and the annular point of ignition must be as narrow as possible in order to obtain a maximum effect. Accordingly, this invention relates to an explosive charge with an annular ignition gap formed by the initiating element or primer having a width of only 1-5 mm.

It is therefore an object of the present invention to provide an explosive charge having an annular ignition charge which eliminates or otherwise avoids the disadvantages inherent in known arrangements of a similar type.

It is another object of the present invention to provide an explosive charge having an annular ignition charge which insures a symmetrical propagation of the detonation waves.

It is a further object of the present invention to provide an explosive charge having an annular ignition charge which is within a prescribed range of thickness and provides an annular ignition gap of proper width to insure an optimum efficiency in ignition of the charge.

These and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the invention when taken with the accompanying drawing which provides a longitudinal sectional view of an explosive charge in accordance with the invention.

In the drawing, a hollow blasting charge with means to effect annular initiation thereof is shown in accordance with the invention. The explosive charge 1 is provided in a cartridge or container which includes a cavity 2 having a lining 3 joining with the container jacket 7. The ignition takes place from the primer 4 formed in a thickened end ofjacket 7 with the blasting cap 5 by way of a predominantly conical propagation charge 6, which latter is disposed between the jacket 7 and the conical inert component 8. This propagation charge has a substantially uniform thickness b, and the annular ignition gap 9 exhibits a width a.

In detail, the limits of the dimensions a and b depend .on the high-brisance explosives preferably employed as the explosive 1 in this arrangement. The lower limit for the width a of the annular ignition gap, i.e., the gap between the propagation charge 6 and the hollow explosive charge 1, is determined by the point at which a safe, complete detonation is still ensured. Suitably, the annular ignition gap is a little wider, e.g., about 0.5 1 mm., than the minimum with required for a safe, complete detonation.

Corresponding considerations also apply in connection with the thickness b of the propagating blasting charge 6 itself, which latter likewise is to be only a little thicker than necessary for a sure transmission of the detonation. The optimum thickness of the propagation charge 6, which is preferably conical, is, for example, in case of penthrite, 3 mm., and in case of cyclonite and tetryl, 4-5 mm. The thickness of the various explosives, especially high-brisance explosives, required to attain a safe, complete detonation has been determined by experimenting with bands of various thicknesses, for example, having a width of 3-5 cm. Normally, these values are 2-5 mm. In case of larger wall thicknesses, the initiation is highly scattered and the effect is diminished.

In case of too small a thickness b, a safe propagation of the detonation is no longer ensured, and there is no initiation at all, or only an irregular initiation. Preferably, the thickness or width of the annular ignition gap is equal to the thickness or breadth b of the explosive propagation charge. However, the latter can also be thicker and can be, for example, 4 mm., in case the annular ignition gap has a width a of only 2 mm. The propagation charge can consist of pressed or cast ex- While I have shown and described one embodiment in accordance with the present invention. it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art, and I therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are obvious to one of ordinary skill in the art.

I claim:

1. An explosive device comprising a generally cylindrical explosive charge in a container having one end closed, an inert conical member having its major base in contact with the open end of said explosive charge and being slightly smaller in diameter than said explosive charge so as to leave exposed an annular surface of uniform width forming with said conical member and said container an annular ignition gap, said container being spaced uniformly from the conical surface of said conical member to form an annular initiation space, and propagation charge means disposed in said annular initiation space and filling said ignition gap for ensuring symmetrical propagation of the detonation waves around the major base of the inert conical member, said annular ignition gap having a predetermined width and said propagation charge means having a predetermined thickness, at least one of the predetermined width of said ignition gap and the predetermined thickness of said propagation charge means exceeding the respective minimum width and minimum thickness absolutely necessary to effect sure and safe propagation of the detonation by 0.5 to 1 mm.

2. An explosive device as defined in claim 1, wherein the thickness of said propagation charge means is substantially equal to the width of said ignition gap.

3. An explosive device as defined in claim 2, wherein a blasting cap is supported on the minor base of said conical member in contact with said propagation charge means and a primer charge is supported by container in contact with said blasting cap.

4. An explosive device as defined in claim 3, wherein said closed end of said container includes a conical hollow.

5. An explosive device as defined in claim 2, wherein said propagation charge means is penthrite and its thickness is 3 mm.

6. An explosive device as defined in claim 2, wherein said propagation charge means is cyclonite and tetryl and its thickness is 4 to 5 mm.

7. An explosive device as defined in claim 1, wherein said propagation charge means has a thickness of 4 mm. and said ignition gap has a width of 2 mm.

8. An explosive device as defined in claim 1, wherein the width of said ignition gap is 1 to 5 mm.

9. An explosive device as defined in claim 1, wherein the width of said ignition gap and the thickness of the propagation charge means exceed the respective minimum width and minimum thickness for safe propagation of the detonation by 0.5 to 1 mm. 

1. An explosive device comprising a generally cylindrical explosive charge in a container having one end closed, an inert conical member having its major base in contact with the open end of said explosive charge and being slightly smaller in diameter than said explosive charge so as to leave exposed an annular surface of uniform width forming with said conical member and said container an annular ignition gap, said container being spaced uniformly from the conical surface of said conical member to form an annular initiation space, and propagation charge means disposed in said annular initiation space and filling said ignition gap for ensuring symmetrical propagation of the detonation waves around the major base of the inert conical member, said annular ignition gap having a predetermined width and said propagation charge means having a predetermined thickness, at least one of the predetermined width of said ignition gap and the predetermined thickness of said propagation charge means exceeding the respective minimum width and minimum thickness absolutely necessary to effect sure and safe propagation of the detonation by 0.5 to 1 mm.
 2. An explosive device as defined in claim 1, wherein the thickness of said propagation charge means is substantially equal to the width of said ignition gap.
 3. An explosive device as defined in claim 2, wherein a blasting cap is supported on the minor base of said conical member in contact with said propagation charge means and a primer charge is supported by container in contact with said blasting cap.
 4. An explosive device as defined in claim 3, wherein said closed end of said container includes a conical hollow.
 5. An explosive device as defined in claim 2, wherein said propagation charge means is penthrite and its thickness is 3 mm.
 6. An explosive device as defined in claim 2, wherein said propagation charge means is cyclonite and tetryl and its thickness is 4 to 5 mm.
 7. An explosive device as defined in claim 1, wherein said propagation charge means has a thickness of 4 mm. and said ignition gap has a width of 2 mm.
 8. An explosive device as defined in claim 1, wherein the width of said ignition gap is 1 to 5 mm.
 9. An explosive device as defined in claim 1, wherein the width of said ignition gap and the thickness of the propagation charge means exceed the respective minimum width and minimum thickness for safe propagation of the detonation by 0.5 to 1 mm. 